True to form, Sunday night's MTV Movie Awards were a fizzy, freewheeling affair. The show, after all, is less a ceremony celebrating actors and their craft than it is an excuse for them to plug upcoming movies and try their hand at viral stunts.

Here are six of the show's most memorable moments, for better or worse.

Conan's 50-cameo opener: In what seemed like an attempt to add some star power to the show (which isn't exactly an A-list destination) and to one-up Ellen DeGeneres' famous Oscar selfie, Movie Awards host Conan O'Brien kicked things off with a video skit featuring cameos from 50 celebrities in five minutes.

After the setup for the skit, which involved O'Brien talking to a room of white-haired MTV execs and challenging himself to pull off the star-studded task, he raced through a series of one-off gags with celebrities as Jessica Alba, Seth Rogen, Russell Crowe, Taylor Swift, Martin Scorsese and Lupita Nyong'o. It was funny, and also one of the last times we saw Conan all night.

Sunday night, he proved true to his word, thanks to an assist from presenter Rita Ora. After imploring Efron to "take it off," Ora sneaked behind Efron, who made a half-hearted show of reluctance, and ripped his shirt open mid-speech, prompting squeals from the audience. Efron then enthusiastically removed his shirt and flexed before departing the stage.

Channing Tatum celebrated, silenced: Honored guest Channing Tatum was this year's recipient of MTV's Trailblazer Award, which is given to actors who … actually, we're not sure just what the award signifies, and neither was presenter (and "22 Jump Street" costar) Jonah Hill, who joked, "What's a more trailblazing experience than a gorgeous man becoming a movie star?"

Accepting the award, Tatum seemed genuinely humbled and said, "I'm not really sure what I did to deserve this. It's weird because 10 years ago I was sitting in front of my TV watching this show … I didn't have the faintest thought I could actually be standing up here talking to y'all. I had no idea if I'd be good at anything, much less acting."

Tatum quickly wrapped up his speech, claiming he had been subjected to O'Brien's version of wrap-up music: a nude selfie flashed on the teleprompter. "I got the .. pic, so I gotta go," Tatum said. "I love you guys."

Best kiss — or rather, worst: Efron also popped up in one of the show's more cringe-worthy skits, setting up the award for best kiss. Presenters Efron, Dave Franco and Seth Rogen announced that they would each kiss a random audience member, and Efron and Franco found themselves coupled with attractive young ladies. Rogen, however, protested when he saw his kissing partner: "Wait a minute, that's my mom!"

Rogen and the alleged Mrs. Rogen then performed an aggressive, obviously staged and still unseemly lip-lock. (The moment beat out another squirmy scene when "The Other Man's" Cameron Diaz, Kate Upton and Leslie Mann, in a bit that featured an elaborate moment of staged sexiness, presented an award to Josh Hutcherson in which Diaz called the actor's pic "The Hunger Games: Catching Fires.")

The Movie Awards gets serious: Amid all the disrobing and awkward kissing, the show did feature a few welcome moments of solemnity. "Dallas Buyers Club's" Jared Leto, accepting the award for best on-screen transformation, spoke about the ongoing battle against AIDS.

"We've made a lot of progress in the battle against AIDS, but it's not time to celebrate just yet," he said. "There's no cure; the epidemic rages on. But here's to the hope that one day we'll put an end of this plague."

While accepting the prize for movie of the year on behalf of "The Hunger Games: Catching Fire," Hutcherson paid tribute to the late Philip Seymour Hoffman. "I know that if Phillip were here, he would think this was really cool," he said. "We think about him every day on set. Wherever he is, this definitely goes out to him."

The show also featured a tribute to the late "Fast and Furious" star Paul Walker, during which costar Vin Diesel said, "The world saw his magic on-screen, the world saw his philanthropic endeavors, yet I wish the world could've seen how special a brother he was."

Mark Wahlberg, senior citizen:"Transformers: Age of Extinction" leading man Mark Wahlberg was on hand to receive his Generation Award, MTV's version of a lifetime achievement award. Or as he characterized it, the "Too ... Old to Return Award!"

Naming such previous recipients as Jim Carrey, Ben Stiller and Adam Sandler, Wahlberg said, "Do you know what they all have in common? None of them were invited back. They're all too ... old!"

But, he added, "It was a great run, and I'm a lucky guy in so many ways." And, of course, he managed to tout his upcoming "Transformers" and "Entourage" movies.